Separation of mixed c8 aromatic hydrocarbons into xylene and ethylxylene



, 0d 9 .1956 D. A. MocAULAY E1' AL 2,766,305

SEPARATION OF MIXED C6 AROMATIC HYDROCARBONS INTO XYLENE AND ETHYLXYLENEFiled Sept. 30. 1952 n a N www. n nM/1. M .N .P. m IA Mm@ Nui WH 0Anited States Patent SEPARATIN F MIXED Cs AROMATIC HYDRO- CARBONS INTOXYLENE AND E'I'HYLXYLENE` David A. McCaulay, Chicago, lll., and ArthurP. Lien, Highland, Ind., assignors to Standard (lil Company, Chicago,Ill., a corporation of Indiana Application September 30, 1952, SerialNo. 312,281

6 Claims. (Cl. 26o-668) This invention relates to the preparation of1,3-dimethyl-S-ethylbenzene (1,3,5-ethylxylene) by the interaction ofethylbenzene and a xylene isomer. More particularly it relates to theseparation of a feed comprising essentially Ca aromatic hydrocarbonsinto a xylene fraction that is low in ethylbenzene content and asubstantially pure 1,3,5-ethylxylene fraction.

While polystyrene is an excellent plastic for many uses, it has thedisability of the relatively low softening point of about 90 C. Effortsto increase this softening point have resulted in the use ofmethylstyrene and dimethylstyrene as the monomers for the plasticformation. Recently 1,S-dimethyl-S-ethylbenzene (1,3,5-ethylxylene) hasassumed importance as a source of high softening point polystyrene-typeplastic.

In nature 1,3,5-ethylxylene is closely associated with the otherisomeric ethylxylenes and with diethylbenzene. Owing to the fact thatthese aromatics have very similar boiling points, it is impractical toseparate such a natural mixture by fractional distillation. The simplestmethod of obtaining 1,3,5-ethylxylene appears to be synthesis from otheraromatic hydrocarbons.

It is an object of this invention to prepare 1,3,5-ethylxylene by theinteraction of ethylbenzene and a xylene isomer. Another object is thepreparation of 1,3,5-ethylxylene by the treatment of a naturallyoccurring Cs 'aromatic hydrocarbon mixture. A particular object is thetreatment of a feed comprising essentially a Ca aromatic hydrocarbonmixture containing ethylbenzene and at least one xylene isomer toproduce substantially pure 1,3,5-etbylxylene land a xylene fraction thatis low in ethylbenzene content. A particular object is the treatment ofa feed comprising essentially a mixture of ethylbenzene and isomericxylenes to produce substantially pure 1,3,5-ethylxylene and a highpurity m-xylene product fraction.

There is described in our Patent 2,661,382, issued December 1, 1953, oncopending application, Serial No. 23 8,498, filed July 25, 1951, andentitled Preparation of Ethylxylenes a process for the preparation of1,3,5- ethylxylene by the interaction of ethylbenzene and at least onexylene isomer. In that application it is asserted that substantiallydiethylbenzene-free ethylxylene can be obtained only by contacting afeed consisting essentially of a xylene and ethylbenzene, wherein thexylene/ ethylbenzene ratio is greater than 1, with liquid HF in anamount of at least about 2 mols per mol of xylene, and

with BFS in an 'amount between about 0.7 mol and less t than l mol permol of xylene in said feed at aV temperature of less than 160 F. for atime sufficient to produce a 1,3,5-etl1ylxylene containing product. Theamount of BF.; is so adjusted that the liquid HF contains dissolvedxylene complex, free-xylene in physical solution and dissolvedethylbenzene. It is asserted in that application that only under theseconditions is it possible to avoid the formation of diethylbenzeue andthe production of a mixture of diethylbenzene and ethylxylene as the Cio`aromatic hydrocarbon product.

It has now been discovered that it is possible to obtain1,3,5-ethylxylene free of diethylbenzene by reacting ethylbenzene andxylene in the presence of a defined amount of liquid HF and BFa suchthat no free-xylene exists in physical solution in the liquid HF.

It has been found that a critical relationship of ternperature andcontact time exists, which relationship permits the production ofsubstantially pure 1,3,5-ethylJ xylene by the interaction ofethylbenzene and xylene even though all of said xylene is present in thecontacting zone in the form of a xylene-BFa-HF complex. Thus 1,3,5-ethylxylene that is free of diethylbenzene `can be prepared by theinteraction of ethylbenzene and a xylene wherein the mol ratio of xyleneto ethylbenzene is at least 1 in the presence of at least l mol of BFSper mol of xylene, and a suicient amount of liquid HF to form a singlesubstantially homogeneous liquid phase in said reaction Zone, at atemperature below about F. for a time suliicient to 'attain anequilibrium condition of 1,3,5- ethylxylene production. A1,3,5-ethylxylene product free of detectable amounts of diethylbenzeneis separable from the mixture of hydrocarbons obtained by the removal ofHF and BFs therefrom.

It has been found that the treatment of a mixture of ethylbenzene and axylene with a sufficient amount of BFa .to complex all of said xylene,i. e., 1 mol per mol of said xylene, Iand sufficient liquid HF toparticipate in the complex formation and to dissolve said complex andsaid ethylbenzene at a given temperature results in either (l) a mixtureof diethylbenzene, xylene, benzene and ethylbenzene, or (2) a mixture ofdiethylbenzene, ethylxylene, xylene, benzene and ethylbenzene, or (3) amixture of ethylxylene, xylene, benzene and ethylbenzene. Thedisproportionation of ethylbenzene to diethylbenzene and benzene appearsto occur 'as 'a very rapid first reaction. After the formation of thediethylbenzene and its solution in the liquid HF in the form of adiethylbenzene- BFs-HF complex, there occurs a very slowdepending on thetemperatureinteraction between diethylbenzene and xylene to formethylxylene and ethylbenzene. By allowing a suiiciently long contactingtime an equilibrium condition is attained wherein all the diethylbenzenehas interacted to produce Ia mixture of ethylxylene, benzene, xyleneIand ethylbenzene.

It has further been found that an appreciable period of time existsbetween the formation of the diethylben- Zene and the appearance of adetectable amount of ethylxylene. By taking advantage of this inductionperiod it is possible to treat a mixture of Cs aromatic hydrocarbons toproduce essentially pure diethylbenzene and a xylene that issubstantially free of ethylbenzene. This process of ethylbenzeneconversion to diethylbenzene in the presence of Xyleues is the subjectmatter of our copending application, Serial No. 312,278, filed September30, 1952, now abandoned, and entitled Separation of Mixed Cs AromaticHydrocarbons into Ethylbenzene 'and Xylene.

In the process of this invention at least l mol of BFs is present in thereaction zone per mol of xylene charged to the reaction zone, i. e.,suliicient BFx is present to complex all of the xylene charged. Morethan this minimum amount is preferred and as `much as 5 mols of BF3 permol of xylene may be used. It is preferred to use between about 1.5 and3 mols of BFs per mol of xylene charged. t

The process of this invention must be carried out under substantiallyanhydrous conditions. The liquid HF used in the process should besubstantially anhydrous, i. e., the liquid HF should contain less than 2or 3% of water.

The amount of liquid HF present in the process must be sulficient todissolve the complex formed and the ethylbenzene as Well as toparticipate in the formation of much as 50 mols.

the complex. It is necessary to use at least about 2 mols of liquid HFper mol of Cs hydrocarbon in the feed. More than this minimum amount isdesirable, e. g., as It is preferred to use in this process betweenabout 6 and 15 mols of liquid HF per mol of Cs aromatic hydrocarbon inthe feed.

It has been found that the higher the temperature of contactingV theshorter the contacting time necessary 'to produce an equilibrium1,3,5-ethylxylene condition in the substantial absence ofdiethylbenzene. Temperatures high as 200 F. may be `used lif the contactt is shortened, preferably if the reaction is halted by a quenchingoperation in order to avoid side reactions such as hydrogen transfer. Ingeneral the practical maximum upper temperature limit is about 160 F.Temperatures beiow ambient maybe used if the necessarily prolongedcontacting time is tolerable. For example, suitable Contact ing 'timesatvarious 'temperatures are: 60 F., about 5:3 hours; 100 F., about 6hours; 120 F., about 3 'ii-ours; 150 F., about 30 minutes.

lt is preferred to operate at a temperature between about 120 and 150 F.for a time between about 3 hours and about 30 minutes, where the longertimes correspond to the lower temperatures. This preferredtemperaturetime relationship appears 'to give reasonabie reaction timeswith the least amount of side reactions.

It is to be understood that the reaction is an equilibrium phenomenonand that even at high temperature and long contacting time someethylbenzene will remain unconverted. At the preferred conditions ofliquid HF and EP3 usage and the preferred temperature-time relationship,about 90% of the ethylbenzene in a feed comprising essentiallyethylbenzene and xylene will be converted to 1,3,5-ethylxylene. Theunoonverted ethylbenzene normally will be recovered along with thexylene. However, when operating on a naturally occurring Cs aromatichydrocarbon mixture such as a hydroformate or a platformate cut, theproduct xylene fraction will be low in ethylbenzene and usually will bea high purity xylene,

i. e., the xylene fraction will contain about 5% or less of ethylbenzeneSubstantially liquid HF-insoluble hydrocarbons such as paraiiins andnap'hthenes readily wash ethylbenzene out of Solution fromcomplex-containing liquid HF. A close-boiling mixture of Ca aromatichydrocarbons and non-aromatic hydrocarbons such as is obtained bydistillation of a hydroformate will normally contain about 50 volumepercent of nonaromatic hydrocarbons such as parafiins, naphthenes andoleiins in addition to small amounts of organic sulfur compounds. Bysuperfractionation it is possible to obtain a Cs aromatic hydrocarbonconcentrate which contains on the order of 90% of aromatic hydrocarbonsconsisting of ethylbenzene, xylene isomers and minor amounts of C9aromatic hydrocarbons. When a Cc aromatic hydrocarbon feed such as isdescribed in this paragraph is contacted with a sufficient amount ofliquid HF and at least about 1 mol of BFS per mol of aromaticVhydrocarbon in the feed, a raffinate phase and an extract phase areformed. The raffinate phase vcontains essentially all the non-aromatichydrocarbons. It has been found that regardless of the amount ofcontacting carried out between the raffinate phase and the extract phaseconsiderable amounts of ethylbenzene Will be present in the raffinatephase.

Even when treating a feed containing as little as 10 volume percent ofnon-aromatic hydrocarbons between about and 30% lof the ethylbenzenepresent in the feed will be found in the rainate phase. Apparently thepresence of non-aromatic hydrocarbons as a separate raflinate phase Veryadversely affects the ability of the liquid HF-BF3 treating agent toconvert and maintain ethylbenzene in the extract phase in the form ofdiethylbenzene suitable for interaction to ethylxylene. (Ethylbenzenerecovery by extractive distillation processes or other extractiveprocesses from the rafnatephase is not 4 considered as recoverableethylbenzene within the meaning of this invention.)

The presence of benzene fand toluene markedly reduces the degree ofconversion to ethylxylene.

The presence of dissolved non-aromatic hydrocarbons and dissolved and/or complexed organic sulfur compounds in the acid phase does not appearto adversely affect the reaction of ethylbenzene to diethylbenzene and,subsequently, to ethylxylene. The solubility of nonaromatic hydrocarbonsin liquid HF is increased some what by the presence of an aromaticcomplex in the liquid HF. The concentration of complex in the liquid HFincreases the amount of non-aromatic hydrocarbon soluble in said complexcontaining liquid HF. However, it has been found that under theconditions of liquid HF and BFS usage described above, that not morethan on the order of 23 volume percent of non-aromatic hydrocarbons canbe tolerated in the Vfeed if operation without a raflinate phase in thecontacting zone is desired. The maximum content of non-aromatichydrocarbon will be dependent on the amount of liquid HF used andsomewhat on the amount of Bib` used. It is preferred to operate with aminimum of non-aromatic hydrocarbon in order to improve the purity ofthe xylene product fraction. The preferred feed stock to the processcomprises essentially a mixture of at least one xylene iso-mer andethylbenzene, i. e., the feed stock contains less than about 2 volumepercent of non-aromatic hydrocarbons and the naturally occurring amountsof organic sulfur compounds.

Feed stocks obtained from the so-called hydroforming and platformingprocesses, i. e., hydroformates or platformates, contain 'some smallamounts of olefms. These olenns readily alkylate some of the aromatichydrocar- 'bons and form alkyl aromatics which have a boiling pointhigher than the ethylxylene product and may be readily separatedtherefrom by distillation. The organic sulfur compounds present in feeds'from hydroformatcs and platformates are readily removed from theproduct hydrocarbons by treatment with sulfuric acid or with anhydrousliquid HF.

The non-aromatic hydrocarbons, other than olens, present in a mixed feedboil in about the same range as the xylene isomers. As a consequencethese non-arou matic hydrocarbons are concentrated in the product xylenefraction. However, even when operating with a maximum of about 2-3volume percent of non-aromatics in feed, the 'product xylene fractionwill contain 5% or less of non-aromatic hydrocarbons. This is considereda high purity xylene product and is usable in most operations requiringVhigh purity xylene. .lt has been found that the close-boilingnon-aromatic content can be decreased by washing of the complexcontaining iquid HF solution with an inert liquid hydrocarbon diluentsuch as butano, Vpentane or hexane which lhasV a different boiling pointthan the desired products. ri`he ethylxylene complex is so stable thatsubstantially no adverse side reactions talce place such as occur in thewashing of a diethylybenzene complex-containing liquid HF. -Excessiveamounts of wash liquid should be avoided. Suitable amounts will vary butin general between about l0 and 10Q volume percent, based on feed, maybe used.

Although it is preferred to operate the process using a feedstockandamounts of liquid HF and BFS such that ,substantially only one liquidphase is present in the contacting zone, it is to be understood thatsome gaseous BFS will'be present under all operating conditions. in thecontacting Zone the term single substantially homogeneous liquid phaseis to be understood as including (a) conditions such that only a liquidHF solution is present or (b) such that a barely detectable amount ofraffinate phase is present along with the liquid HF solution.

The amount of ethylbenzene and xylene present in the reaction Zone has alarge effect on `the yield of the sired ethylxylene. The mol ratio ofxylene to ethylben* zene in the feed to the process should be at' least1 and preferably greater than 1, e. g., as much as 10. It is preferredto operate on a feed wherein the ratio of xylene to ethylbenzene is atleast about 3. Normally the xylene/ ethylbenzene ratio present in anaturally occurring mixed Cs aromatic hydrocarbon fraction will besuitable for operation within the preferred ratios of the process.However, some unusual natural fractions have a very high ethylbenzenecontent; such a fraction is readily brought within the preferredoperating ratio by the addition of xylene to the fraction.

The annexed drawing, which forms a part of this speciication,illustrates one embodiment of this invention. The embodiment shown isschematic and many items of process equipment, such as, pumps andvalves, have been omitted; these may be readily supplied by thoseskilled in the art.

The feed to this illustration was derived from a Cs aromatic cut,boiling between 270 and 300 F., of a hydroformate. This cut containedabout 12% of non-aromatic hydrocarbons. The non-aromatic hydrocarboncontent was reduced to about 2 volume percent by means of an extractivedistillation with phenol as the separating agent. The C3 feed consistsessentially of 2 volume percent of non-aromatic hydrocarbons, whichincludes a trace of oleins and organic-sulfur compounds (a total sulfurcontent of about 0.01%), less than 1 mol percent of C9 aro-- matichydrocarbons and the remainder C3 aromatic hydrocarbons. The Cs aromatichydrocarbons consist of: ethylbenzene, 12%; o-xylene, 21%; m-xylene,48%; and p-xylene, 19%.

The feed from source 11 is passed through line 12 into mixer 13. BFSfrom source 16 is passed by way of lines 17 and 1S into mixer 13; inthis illustration, 2 mols of BFa per mol of xylene in mixer 13 arepresent therein. Substantially anhydrous liquid HF from source 21 ispassed by way of lines 22 and 23 into mixer 13; in this illustration 9mols of HF are present in mixer 13 per mol of aromatic hydrocarbonpresent therein.

Mixer 13 is provided with heat transfer coil 26. The complex formationis exothermic and coil 26 permits withdrawal of this heat or permits theadjusting of the temperature of the materials to the desired contactingtemperature. The materials are withdrawn from mixer 13 and are passed byway of line 27 into reactor 31.

Reactor 31 is a vessel provided with heat exchangers 32 and 33 whichmaintain the temperature therein at the desired point. Since a singleliquid phase exists in reactor 31 no agitating means are provided. Thefeed and liquid HF-BFs agent are maintained in reactor 31 at 150 F. for30 minutes. The materials are passed from reactor 31 by way of line 34into extractor 36.

Extractor 36 is an upright vessel provided with contacting means, suchas, Berl saddles, Raschig rings or trays. In extractor 36, the liquid HFsolution is contacted with pentane to extract unconverted ethylbenzene,benzene, uncomplexed C9 aromatics and the non-aromatics. Extractor 31 isoperated at about ambient temperatures by means of the use of coldpentane and a vessel size such that there exists a liquid holdupsufficient to overcome the effect of the introduction of hot HFsolution. (A cooler may be inserted in line 34, if desired.) Extractor36, reactor 31 and mixer 13 are operated at superatmospheric pressure inorder to keep the HF in the liquid state. Pentane from source 37 ispassed through line 38 into extractor 36, near the bottom thereof, Inthis illustration about l() volume percent of pentane is added `based onCs feed to the process.

The pentane-rich raiinate phase is withdrawn from the top of extractor36 by way of valved line 39 and is passed to gas separator 41. By theuse of a large excess of BFs and low extraction temperature, the loss ofxylene to the raflinate phase is minimized. BFs is withdrawn fromseparator 41 and is cycled to mixer 13 by way of line 42, for reuse inthe process. The raflinate phase is passed through line 43 into stripper44.

Stripper 44 is a fractionating device, provided with an internal heater46. A EP3-saturated pentane fraction is taken overhead from stripper 44and is recycled to extractor 36 by way of line 47, condenser 48 andlines 49 and 38. A pentane-free bottoms fraction is passed from stripper44 by way of line 51 into fractionator 52.

Fractionator 52 is provided with an internal heater 53. Fractionator 52separates an essentially pure benzene fraction overhead, which is passedto storage not shown, by way of line 56. A mixture of ethylbenzene(about 10% of that present in the feed), the closeboiling nonaromaticsand some C9 aromatic hydrocarbons are withdrawn as a bottoms productfrom fractionator 52 and sent to storage, not shown, by way of line 57,This ethylbenzene fraction may be used as a component of high octanegasoline or the ethylbenzene content may be recovered by an extractivedistillation process.

The extracted liquid HF solution is withdrawn from the bottom ofextractor 36 through line 61 and is introduced at about the mid-point ofdecomposer 62. Decomposer 62 is provided with an internal heater 63 anda few fractionating trays. Decomposer 62 may be operated at below theboiling point of HF or at elevated temperatures, such as 150 F. Herein,decomposer 62 is operated at a top temperature of about F. under aslight vacuum, so that only HF and BF3 are withdrawn overhead. The HFand BFs are passed through line 66, vacuum pump 67, line 68 into cooler69.

In cooler 69 the HF is condensed and the liquid HF and gaseous BFs arepassed through line 71 into gas separator 72. Gaseous BFS is withdrawntherefrom by way of valved line 73 and is cycled to mixer 13 throughline 18. Liquid HF is withdrawn therefrom by way of valved line 74 andcycled to mixer 13 by way of line 23. The BFa gradually becomescontaminated with HzS from the decomposition of organic-sulfurcompounds; occasionally BFs must be withdrawn from the system andpurified by processes well known to the art.

A mixture of m-xylene, some ethylbenzene, 1,3,5 ethylxylene and somehigher boiling aromatics is withdrawn from decomposer 62 and passedthrough line 76 into fractionator 77, provided with internal heater 78.A m-xylene fraction that contains negligible amounts of ethylbenzene andsulfur compounds is withdrawn overhead and sent to storage, not shown,by way of line 79.

This xylene fraction also contains some pentane, which can readily beremoved 'oy distillation, if desired. (Decomposer 62 can be operated toremove pentane overhead; the pentane can be separated from the HF byinserting a liquid settler in line 71.)

A bottoms fraction that consists of 1,3,5-ethylxylene and some slightamount of Cs aromatic and higher boiling aromatic hydrocarbons iswithdrawn and sent to storage, not shown, by way of line 81.

It may be desirable at times to accept a. lower yield of ethylxylene inorder to decrease contacting time or to operate at a lower temperature.For example, operation at F. for a contacting time of 2O minutes willproduce a C10 aromatic product containing a large amount ofm-diethylbenzene as well as the desired 1,3,5- ethylxylene. Thediethylbenzene cannot be separated by distillation. The diethylbenzene,if recovered separately, can be recycled to the feed and will increasethe overall yield of ethylxylene. It has been found thatm-diethylbenzene can be separated from 1,3,5-ethylxylene by means ofliquid HF and BFS. By diluting the Cio aromatic fraction with about anequal volume of pentane and then contacting this feed in an extractiontower with sufficient liquid HF to form an extract phase, e. g., about6-15 mols, and with 1 mol of BFs per mol of 1,3,5- ethylxylene in thefeed, a rainate phase and an. extract phase are obtained. With properuse of ethylxylene reux and about 5 theoretical extraction stages, it ispossible to obtain a m-diethylbenzene product containing about 1% ofethylxylene and a 1,3,5-ethylxylene product cou- Amerized to m-xylene.

taining about 1% of m-diethylbenzene, i. e., high purity products. Thism-diethylbenzene product is then sent to mixer 13.

,In order to show some of the results obtainable by theprocess, thefollowing experimental runs are described.

These runs were carried out using a carbon steel reactor provided with a1725 R. P. M. stirrer. In all runs the order of addition was: (l) feed,(2) liquid HF, and (3) EP3. VThe contents of the reactor were brought tothe desired temperature and were agitated for the desired contactingtime. At the completion of the contacting time the stirring was stoppedand the contents permitted to settle for about minutes. The contents ofthe reactor were withdrawn in such a manner that two liquid phases (ifany existed therein) were withdrawn into separate receivers. The liquidphase(s) was withdrawn into a copper vessel filled with crushed ice. Thedecomposition of the complexes by the water resulted in the formation ofa lower aqueous `layer andan upper hydrocarbon layer. with diluteaqueous caustic to remove HF `and B153 remaining therein and then waterwashed to remove traces of the aqueous caustic.

TABLE 1 Run No I II vIII Temperature, F 68 145 75 Contacting Time,Minutes 90 30 30 Reactor Charge, Mols:

2.41 0.82 A O. 81 ethylbenzene 1.22 0. 83 0. 8l n-heptane (Vol. Percenton feed) Nenn None (50%) F 22. 5 30.0 3. 34 2. 7

(Mols) (Percent) Total Refi Ext Product Distribution, Mol

Percent:

Benzene 22.1 19. 7 0.12 0.10 0.0 \,lcnc 37. 7 54.0 0.06 1.05 45.4 lene.9. 8 0. 37 0.11 19. b l`oenzene.. 12. 3 3.4 0. 36 0 07 17. 5 dihylbonzene 1 17. 6 0.17 6.0 ethylxyleno 2 1. 2 22.9 0.02 0.8 C12aromaties. 0.02 0. 8 .Ethyl'nonzcno Conversion,

Percent 75 87 (85) 50 l Within experimental error, 100% mota-isomer.

` Run 1 shows that when using a xylene/ethylbenzene ratio of 1, andabout 2 mols of BF3 per mol of xylene, a contacting time of 90 minutesat 68 F. resulted in only a very low yield of etbylxylene. Under theseconditions the conversion of ethylbenzene was relatively low. Also ofinterest is the fact that about 80% of the p-xylene was converted.either to ethylxylene or was iso- Within experimental error thediethylbenzene and ethylxylene product fractions consisted of.1,3-diethylbenzene, i. e., the meta-isomer and the 1,3-dimethyl-.S-ethylbenzene isomer of ethylxylene.

The hydrocarbon layer was washed 9 Run II shows the effect of operatingat high temperature in regard to the production of an ethylxylenefraction which contains no :detectable amount of diethylbenzene. Thecontacting time of 30 minutes used in this run is believed to be longerthan necessary for the attaining of equilibrium conditions. Thexylene/ethylbenzene ratio of 3 markedly improved the ethylbenzeneconversion over Run I.

Run III is presented to show the effect of a non-aromatic hydrocarbondiluent on both the direction of the reaction and the overall yields.The data show that with 50% of n-heptane, based on feed, present in thefeed, two liquid phases existed in the reactor. The distribution ofaromatic hydrocarbons in the raflinate phase show that almost 50% of theethylbenzene passed into the raflinate phase as well as about 25% of thexylene in the feed. This latter in spite of the fact that a considerableexcess of BFS over the theoretical 1 mol per mol of xylene was presentin the reactor. Further, it is of interest that more than half thebenzene produced in the reaction passed into the raffinate phase.

Further, Run III shows that under these conditions a side reactionleading to the formation of C12 aromatics, predominantlytriethylbenzene, took place. Further, the results show that despite thefact that of the ethylbenzene in the extract phase was converted, theoverall conversion was only 50%.

In order to determine the solubility of non-aromatic hydrocarbons incomplex-containing liquid HF, two runs were made. In these runs thearomatic hydrocarbon chosen was mesitylene, since it forms a very stablecomplex with HF and BFs. The non-aromatic hydrocarbon in these runs wasn-heptane.

Run IV In this run ml. (1.22 mols) of mesitylene and 25 ml. of n-heptanewere contacted with 25 mols of liquid HF and 1.03 mols of BFs for 45minutes at 70 F. The contents of the reactor were settled for 60 minutesand then withdrawn. Two phases were present in the reactor.

The hydrocarbons recovered from the raffinate phase consisted of 21.3ml. of n-heptane and 13.5 ml. of mesitylene. The hydrocarbons from theextract phase consisted of 3.7 ml. of n-heptane and 156.5 nil. ofmesitylene (1.13 mols). Thus the extract hydrocarbons contained 2.4volume percent of non-aromatic hydrocarbon. It is of interest that therewas present in the extract phase 0.1 mol of mesitylene more than thetheoretical amount of 1.03 mols. (It has been found that 1 mol ofmesitylene and 1 mol of BFa are present in a mesitylene-B Fs-HFcornplex.)

Run V This run was carried out to see if a feed corresponding to theextract hydrocarbons of Run IV could be treated to form a single liquidphase. Thus 171 ml. (1.23 mols) of mesitylene and 3.7 ml. of n-heptanewere contacted with 25 mols of liquid HF and 1.03 mols of BFs under thesame conditions as described in Run TV. When the contents of the reactorwere withdrawn only a single phase was found to be present therein. Thusit was possible to form a single liquid phase by treating a feedconsisting of 2.1 volume percent of non-aromatic hydrocarbon and theremainder polyalkyl aromatic hydrocarbon by the use of only 0.85 mol ofBFs per rnol of aromatic hydrocarbon in the feed. The solubility ofmesitylene in liquid HF alone is about 3 volume percent. Thus about 15rnl. of mesitylene could be dissolved in addition to the amountcomplexed. Thus about 16 Inl. of mesitylene were brought into solutionthrough the solubilizing action of the complex. Heptane is substantiallyinsoluble in liquid HF alone so that virtually the entire amountdissolved in the complex containing liquid HF is due to the solubilizingaction of the complex.

Thus having described the invention, what is claimed is:

1. A process for the treatment of a feed mixture consisting of Caaromatic hydrocarbons containing ethylbenzene and at least one xylenewherein the xylene/ ethylbenzene mol ratio is between at least 1 andabout 10 to produce 1,3,5-ethylxy1ene as essentially the only C10aromatic hydrocarbon and a product xylene fraction low in ethylbenzene,which process comprises contacting said feed with between at least 1 andabout 5 mols of BFs per mol of xylene in said feed and with betweenabout 2 and 50 mols of liquid HF per mol of aromatic in said feed, at atemperature below about 160 F. for a time about su'lcient to attain anequilibrium condition in the formation of 1,3,5-ethylxylene, removing HFand BFS to recover a mixture of hydrocarbons, and separating C aromatichydrocarbon fraction consisting of essentially pure 1,3,5- ethylxylenefrom said mixture.

2. The process of claim 1 wherein said feed consists of a naturalmixture of Cs aromatic hydrocarbons and not more than about 2 volumepercent of non-aromatic hydrocarbons.

3. The process of claim 1 wherein the xylene/ethylbenzene ratio in saidfeed is between about 3 and 6.

4. The process of claim 1 wherein said contacting is carried out betweenabout 60 and 150 F. for a time between about 30 minutes and 50 hours,the longer times corresponding to the lower temperatures.

5. A process for the treatment of a Cs aromatic hydrocarbon fraction toproduce a 1,3,5-ethylxy1ene product and a m-xylene product that isessentially ethylbenzene-free, which process comprises contacting a feedconsisting of ethylbenzene, xylene isomers and not more than about 2voiume percent of close-boiling non-aromatic hydrocarbons wherein themol ratio of xylenes to ethylbenzene is greater than about 3, withbetween about 1.5 and 3 mols of BFa per mol of xylene in said feed andwith between about 6 and 15 mols of liquid HF per mol of aromatichydrocarbon in said feed, at a temperature between about 120 and 150 F.for a time between about 3() minutes and 5 hours, the longer timescorresponding to the lower temperatures to produce a liquid HF solutioncontaining complexed m-xylene and 1,3,5-ethylxylene, unconvertedethylbenzene, benzene and said non-aromatics, extracting said solutionwith sufficient inert hydrocarbon diluent boiling outside the Xylene andethylxylene range to remove substantially all of said benzene7 saidunconverted ethylbenzene and said non-aromatics, removing HF and BFsfrom said extracted solution to recover a mixture of hydrocarbons, andseparating therefrom a xylene boiling range fraction that issubstantially free of ethylbenzene and xylenes other than m-xylene and aCio aromatic hydrocarbon fraction that is substantially free of isomersother than 1,3,5-ethylxylene.

6. The process of claim 1 wherein the temperature of contacting and thetime of contacting necessary in order to obtain substantial equilibriumin the production of ethylxylene are related as follows:

Temperature, F.: Time, hours References Cited in the tile of this patentUNITED STATES PATENTS 2,394,905 Frey Feb. 12, 1946 2,396,966 PassinoMar. 19, 1946 2,408,753 Burk Oct. 8, 1946 2,521,444 Brooke et al Sept.5, 1950 2,563,826 Elwell et al. Aug. 14, 1951 2,564,073 Lien et al. Aug.14, 1951

1. A PROCESS FOR THE TREATMENT OF A FEED MIXTURE CONSISTING OF C8AROMATIC HYDROCARBONS CONTAINING ETHYLBENZENE AND AT LEAST ONE XYLENEWHEREIN THE XYLENE/ETHYLBENZENE MOL RATIO IS BETWEEN AT LEAST 1 ANDABOUT 10 TO PRODUCE 1,3,5-ETHYLXYLENE AS ESSENTIALLY THE ONLY C10AROMATIC HYDROCARBON AND A PRODUCT XYLENE FRACTION LOW IN ETHYLBENZENE,WHICH PROCESS COMPRISES CONTACTING SAID FEED WITH BETWEEN AT LEAST 1 ANDABOUT 5 MOLS OF BF3 PER MOL OF XYLENE IN SAID FEED AND WITH BETWEENABOUT 2 AND 50 MOLS OF LIQUID HF PER MOL OF AROMATIC IN SAID FEED, AT ATEMPERATURE BELOW ABOUT 160* F. FOR A TIME ABOUT SUFFICIENT TO ATTAIN ANEQUILIBRIUM CONDITION IN THE FORMATION OF 1,3,5-ETHYLXYLENE, REMOVING HFAND BF3 TO RECOVER A MIXTURE OF HYDROCARBONS, AND SEPARATING C13AROMATIC HYDROCARBON FRACTION CONSISTING OF ESSENTIALLY PUR1,3,5ETHYLXYLENE FROM SAID MIXTURE.